2015 Multi-University Training Contest 3 hdu 5325 Crazy Bobo

Crazy Bobo

Time Limit: 6000/3000 MS (Java/Others)    Memory Limit: 131072/65536 K (Java/Others)
Total Submission(s): 1334    Accepted Submission(s): 410

Problem Description

Bobo has a tree,whose vertices are conveniently labeled by 1,2,...,n.Each node has a weight wi. All the weights are distrinct.
A set with m nodes v1,v2,...,vm is a Bobo Set if:
- The subgraph of his tree induced by this set is connected.
- After we sort these nodes in set by their weights in ascending order,we get u1,u2,...,um,(that is,wui<wui+1 for i from 1 to m-1).For any node x in the path from ui to ui+1(excluding ui and ui+1),should satisfy wx<wui.
Your task is to find the maximum size of Bobo Set in a given tree.

Input

The input consists of several tests. For each tests:
The first line contains a integer n (1≤n≤500000). Then following a line contains n integers w1,w2,...,wn (1≤wi≤109,all the wi is distrinct).Each of the following n-1 lines contain 2 integers ai and bi,denoting an edge between vertices ai and bi (1≤ai,bi≤n).
The sum of n is not bigger than 800000.

Output

For each test output one line contains a integer,denoting the maximum size of Bobo Set.

Sample Input

7

3 30 350 100 200 300 400

1 2

2 3

3 4

4 5

5 6

6 7

Sample Output

5

Author

ZSTU

Source

2015 Multi-University Training Contest 3

解题：直接搜索。。。建立有向图时候，小权向大权的连边，然后看看每个每个点，最多能走多少个点。

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <vector>
 #include <cstring>
 #pragma comment(linker, "/stack:1024000000,1024000000")
 using namespace std;
 const int maxn = ;
 vector<int>g[maxn];
 int w[maxn],ret[maxn];
 void dfs(int u) {
     ret[u] = ;
     for(int i = g[u].size()-; i >= ; --i) {
         if(!ret[g[u][i]]) dfs(g[u][i]);
         ret[u] += ret[g[u][i]];
     }
 }
 int main() {
     int n,u,v;
     while(~scanf("%d",&n)){
         for(int i = ; i <= n; ++i){
             scanf("%d",w+i);
             g[i].clear();
         }
         for(int i = ; i < n; ++i){
             scanf("%d%d",&u,&v);
             if(w[u] < w[v]) g[u].push_back(v);
             else g[v].push_back(u);
         }
         memset(ret,,sizeof ret);
         int ans = ;
         for(int i = ; i <= n; ++i){
             if(!ret[i]) dfs(i);
             ans = max(ans,ret[i]);
         }
         printf("%d\n",ans);
     }
     return ;
 }